Investigation of reactivity of Pt basal planes towards glucose electro-oxidation in neutral solution (pH 7): structure-sensitivity dependence and mechanistic study

Glucose electro-oxidation is a topic of great relevance in electrochemistry, especially due to the possibility of using this carbohydrate as a fuel in implantable DGFC cells (Direct Glucose Fuel Cell). In spite of it has already been reported in the 1990s that this reaction is sensitive to the symmetry of surface surfaces, the understanding of the structure-reactivity relationship is not completely elucidated, especially in a neutral medium, in which the particularities at well defined surface of this sensitivity is not reported yet. In this context, this work studies the electro-oxidation of glucose in phosphate buffer solution (pH 7 ~ physiological) on low-index Pt single crystal surfaces, using cyclic voltammetry and in situ FTIR techniques at room temperature, with the aim to investigate the reactivity of surface catalysts in neutral medium, and thus, understand and establish the relation between the reaction reactivity and the surface structure (structure-sensitivity). Under these conditions it is observed that glucose electro-oxidation is strongly dependent of the electrode structure in terms of catalytic activity and reaction mechanism. Pt(110) is the less active surface, due to the highest formation of CO_L, which is strongly adsorbed on (110) sites, poisoning them. Pt(100) is the most active surface and the reaction proceeds through a more complex mechanism. Although the highest formation of CO₂ has been observed on this surface, the major activity of Pt(100) is mainly associated to the production of cyclic carbonate on (100) sites. Among Pt low-index planes, Pt(111) is the less poisoned surface, and this is because on this surface carbonate ring is absent and CO_L generated during the oxidative process is completely stripped out from the surface during the potential scan.